If there are any fixed elements in US Presidential debates, they are the
ghosts of presidents past who hover over proceedings, each invocation of
their name dripping with hidden meaning.

The debate in Denver was no exception, with mentions of Bill Clinton, Ronald
Reagan and Abraham Lincoln.

President Obama made two references to Mr Clinton, hoping not only to profit
from “Slick Willy’s” common touch and immense popularity, but also to draw
parallels between his policies and the Clinton Administration’s economic
success.

Mr Romney, too, is fond of dropping Mr Clinton’s name into speeches, usually
to portray him as an